1. Field of the Invention
This invention relates to a dielectric barrier discharge lamp device.
2. Description of Related Art
As shown in FIG. 1, a known dielectric barrier discharge lamp 2 of a substantially hollow cylindrical shape is comprised of a discharge container 21 made of quartz having an entire length of about 300 mm. A discharge space is enclosed between an inner tube 22 and an outer tube 23 which are arranged coaxially. The inner tube 22 has an inner diameter D1 of 12 to 15 mm and the outer tube 23 has an outer diameter D2 of 24 to 27 mm. The outer surfaces of the inner tube 22 and the outer tube 23 are provided with electrodes 24, 25 made of a metallic net for allowing light to pass therethrough.
A dielectric barrier discharge lamp device used in connection with such a dielectric barrier discharge lamp as described above is constructed such that a plurality of dielectric barrier discharge lamps 2 are arranged in one casing 10. Light radiated from each of the dielectric barrier discharge lamps 2 passes through a glass window 3 arranged in the casing 10 and is radiated onto a processed item W (hereinafter also called a workpiece).
In addition, in the case of a dielectric barrier discharge lamp whose discharge container 21 is filled with xenon or argon or krypton, light radiated from the dielectric barrier discharge lamp 2 is vacuum ultraviolet light. In this case, when oxygen is present around the dielectric barrier discharge lamps 2, the vacuum ultraviolet light is absorbed by the oxygen and is no longer irradiated onto the processed item W. As a counter-measure, the inner side of the casing 10 is therefore purged with nitrogen.
That is, the dielectric barrier discharge lamps 2 are arranged in a space sealed hermetically by the casing 10 and the window 3.
In FIG .2, a cooling block 4 is used for cooling the dielectric barrier discharge lamps 2, and a cooling pipe 6 for cooling medium is used for cooling the cooling block 4. Further, mirrors 5 are arranged for reflecting light radiated from the dielectric barrier discharge lamps 2.
In recent years, as the processed item has become larger and larger, a plurality of dielectric barrier discharge lamps 2 have been arranged in the casing 10 so as to adapt the device to the larger processed item. As a result, the size of the window 3 was increased, and it became quite difficult to manufacture the component for use as the integrally assembled large window. In addition, although the component for use as the integrally assembled large-size window was made by melting and molding glass substances, the window component had the problem of being difficult to manufacture as regards a uniform transmission factor, and the ultraviolet ray intensity on the processed item became nonuniform.
Further, in the case that the number of dielectric barrier discharge lamps 2 was changed in response to the size of the processed item, it was necessary to reconstruct the casing 10 itself or to prepare a plurality of casings of different sizes in advance.
The present invention has been made in view of the foregoing circumstances, and it is an object of the present invention to provide a dielectric barrier discharge lamp device for uniformly emitting ultraviolet rays on a processed item having an increased surface area.
According to a further object, the dielectric barrier discharge lamp device should be easily adaptable to the size of the processed item by merely changing the number of casings containing the dielectric barrier discharge lamps in response to the size of the processed item.
The dielectric barrier discharge lamp device of the invention is characterized in that at least one dielectric barrier discharge lamp is arranged in a hermetically sealed casing, said casing comprising a hollow longitudinally extending main part that is closed at both ends by end parts, at least a portion of said main part of the casing defining a window allowing light radiated from the at least one dielectric barrier discharge lamp to pass therethrough onto the workpiece. At least one end part of the casing is provided with a passage allowing inert gas to be introduced into the casing. Further, at least one of the end parts is adapted such as to allow loading or unloading of the at least one dielectric barrier discharge lamp. According to the invention, a plurality of casings are arranged side by side with their windows facing the workpiece to be irradiated.
In the dielectric barrier discharge lamp device of the present invention, when the processing area of the processed item is increased, the number of casings having the at least one dielectric barrier discharge lamp arranged therein is correspondingly increased so that a large-size integral window is not required and the size of the window of each of the casings need not be increased. As a result, a relatively small window having a high and uniform transmission factor can be used for each of the casings, and the intensity of ultraviolet rays on the processed item can be made uniform.
In addition, the dielectric barrier discharge lamp device can be easily adapted to the size of the processed item by merely changing the number of casings.